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More on caching

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hadley 2016-08-22 15:36:28 -05:00
parent 545ca5b13c
commit 492007afca
1 changed files with 9 additions and 2 deletions
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@ -291,9 +291,16 @@ Caching the `processed_data` chunk means that it will get re-run if the dplyr pi
`dependson` should contain a character vector of *every* chunk that the cached chunk depends on. Knitr will update the results for the cached chunk whenever it detects that one of its dependencies have changed.
Note that the chunks won't update if `a_very_large_file.csv` changes, because knitr caching only tracks changes within the `.Rmd` file. That means it's a good idea to periodically clear out all your caches and start from scratch by running `knitr::clean_cache()`.
Note that the chunks won't update if `a_very_large_file.csv` changes, because knitr caching only tracks changes within the `.Rmd` file. If you want to also track changes to that file you can use the `cache.extra` option. This is an arbitrary R expression that will invalidate the cache whenever it changes. A good function to use is `file.info()`: it returns a bunch of information about the file including when it was last modified. Then you can write:
Note that I've used the advice of [David Robinson](https://twitter.com/drob/status/738786604731490304) for naming these chunks. It's a good idea to name chunks that create objects after the primary object that they create. That makes it easier to understand the `dependson` specification.
# chunk 1
`r chunk`{r raw_data, cache.extra = file.info("a_very_large_file.csv")}
rawdata <- readr::read_csv("a_very_large_file.csv")
`r chunk`
As your caching strategies get progressively more complicated, it's good idea to regularly clear out all your caches with `knitr::clean_cache()`.
Note that I've used the advice of [David Robinson](https://twitter.com/drob/status/738786604731490304) for naming these chunks. It's a good idea to name chunks that create objects after the primary object that they create because that makes it easier to understand the `dependson` specification.
### Global options